In order to adapt an airbag, in particular a frontal airbag, to a specific accident situation and/or to the size/weight of the passenger to be protected, it has been known to provide a tensioning element, whose first end is connected to the airbag and its second end to a holding device, wherein the connection between the second end of the tensioning element and the holding device detaches upon receipt of an external signal, so that the properties of the airbag can be influenced through it. Such a tensioning element can, in particular, be used to open or close a ventilation opening in the airbag when holding devices are actuated, or to influence the expansion of the airbag.